With the Beast Inside There's Nowhere We Can Hide
by Casteline
Summary: Derek immediately recognizes the dark spirit when he sees it. The problem is, they can't figure out how to get it out of Stiles. Sterek.


_Crossposted to AO3._

_This was written after 3x17 Stilverfinger and thus does not stay true to the episodes that came later. The discovery of Stiles as the nogitsune, the story of how the nogitsune came into being, and how Stiles is saved all deviates from canon. Also, sterek._

_Enjoy._

* * *

Scott had called his pack (he had surprised even himself when he referred to the Twins as _pack_) to gather in his house one evening to discuss the nogitsune. It had been a couple of weeks since they learned about the purpose of the Oni and the existence of the dark spirit, but in that time, they had learned nothing.

"Do you even have a plan?" Aiden asked, a somewhat accusatory tone in his voice.

"Does it even matter?" Ethan asked. "The nogitsune has been 2 steps ahead of us since the beginning. Almost like he knows what we're going to do before we do."

"Dudes, do you want to be included in this or not? You say you want to be pack, but you're mostly just downers," Stiles said.

"Well I'm sorry we can't all be happy-go-lucky in the face of imminent death."

"Maybe its Peter," Lydia suggested, absently tapping her lip. "Or Cora." She paused when she received strange looks from everyone else in the room. "What? Derek is in town, which means they probably came back with him? What if it's one of them?"

"If they were in town, the Oni would have already gone after them," Allison said. "Even as resourceful as Peter is, I don't think he could have fought them off on his own."

"Is anyone else bothered that we haven't seen our masked friends in a while?" Isaac asked.

"I'm personally taking it as a blessing," Stiles said. "Maybe they realized they were looking in the wrong place and went somewhere else."

"Its never that simple," Scott said. His nose twitched and he sat up a little straighter. "Derek is here." A few seconds later, Derek walked in the front door, not bothering to knock. He looked around at the group sitting on the floor. "You're late," Scott said, but Derek wasn't paying any attention to him. He was staring at Stiles, frowning.

"Hey," Stiles said. The longer Derek stared, the more uncomfortable he became. "Any particular reason you're staring at me like a piece of meat? I mean, it's flattering and all, but- ack!" he let out a shriek as Derek grabbed him by the back of his collar and threw him into the nearest wall. "What the hell man!?" The others all jumped to their feet as Derek pinned Stiles to the wall.

"_YOU GUYS HAD BETTER NOT BE FIGHTING DOWN THERE,_" Melissa shouted from upstairs.

"Derek, what are you doing?" Scott asked, his claws extending.

Derek turned back to them, his eyes glowing blue. "Use. Your. Eyes." He turned back to Stiles.

"Dude, what is your problem?" Stiles asked. "You're hurting me."

"I'm sorry," he said, and for a moment, it almost sounded genuine, but then he let out a hair splitting roar.

Scott took a step forward, intent on freeing his friend, but then Stiles' features shifted and hardened. It was not like the wolves shifting; it was still completely Stiles on the outside, but it suddenly became all too clear that it was not all Stiles on the inside. Scott's eyes flashed red and suddenly he could see it. A dark aura surrounding him.

Stiles moved faster than seemed possible, one moment he was pinned under Derek's strong grip, the next Derek was lying on the floor, barely conscious. Aiden and Ethan lunged at him, only to find themselves on the ground as well.

"_DON'T MAKE ME COME DOWN THERE._"

"It's you," Scott said. "It's been you this whole time."

"No one suspected the puny human. Perfect hiding place. Shame you had to find out."

"We'll kill you," Isaac said, baring his fangs.

Stiles laughed, but it didn't sound anything like Stiles. "No, you won't. That's what makes him perfect. You all love him, pity him. Poor, defensless Stiles. He's so full of sadness, and anger, did you know?"

"You're what came through when we did the sacrifice," Allison said.

"And you latched onto the one with the most sadness to feed off," Lydia added.

"Oh, you are all so _simple_. No. I have been here so much longer. Your little ritual just... _opened the door._"

"Okay, door's open. Now what?" Scott asked.

"I'm going to do exactly what I came here to do, and there is nothing you can do to stop me," he said, the fell to the ground, unconscious.

* * *

Derek was still pissed at the twins for thinking it was okay to host a backlight party at his loft. The lights and stereo equipment had been disassembled and removed weeks ago, but the walls were still covered in colorful, weirdly scented paint, and frankly, it was giving him a headache.

No, the headache was likely stemming from the fact that Stiles was possessed by a dark spirit and he had no fucking clue what to do about it.

_'Hey, Derek,' Stiles greeted happily. "I heard you were back in town, but I didn't quite believe it until now."_

_Derek just stared at him for a moment. He really didn't remember anything from their last encounter._

_"Yeah. I've been, uh, busy the past few weeks. Research, and whatnot."_

_"Derek Hale, doing research? I don't think I'll believe it until I see it."_

Derek slammed his book closed, but resisted the urge to throw it across the room. Why couldn't he stop thinking about Stiles?

There was a knock at the door. The smell of the paint assaulting his nose blocked out most other scents, thus he had to resort to the sound of the quick, jagged heartbeat to identify his guest.

"What do you want, Stiles?" he asked, sliding the door open partially. Hs features immediately softened when he saw the look of him. He was upset, and clearly scared. No. Terrified.

"It's me, isn't it?" he asked, his voice shaking.

"What are you talking about?" Derek asked. They had all agreed to this. Stiles' couldn't know. They had to keep him out of the loop in order to keep the nogitsune out, and if Stiles' found out the truth, it would make everything so much worse.

"The dark spirit. It's me."

Derek sighed. He hated secrets, particularly this secret. He opened the door wider to let him in. "How did you find out?"

"Scott looks at me strangely, like he's worried about me. The twins look at me like they want to tear me apart, which is honestly not a huge leap, but Isaac looks afraid of me, and the girls won't even look at me. And you... I don't even know how to begin interpreting the way you look at me. The hallucinations, sleep walking, everything that happened with Barrow, and now everyone is actively keeping me out of plans and discussions. Occam's Razor: I'm the dark spirit. And everyone knows except me."

"Now you know."

"How did you all find out?"

"I could see it. The darkness wrapped around you."

"Like Scott can see Kira's aura?"

Derek nodded. "And when I confronted you, it showed itself."

"I don't remember."

"You wouldn't."

Stiles nodded and started mindlessly rummaging through the stack of books on Derek's desk. "What is all this?"

"Research. Japanese mythology."

"You can read these?" he asked, holding up a few books that were completely in Japanese.

"I took a few semesters of Japanese when I was in New York."

"I can't imagine college student!Derek. What did you study? Aside from Japanese, I mean."

"Mythology and literature. Greek, Roman, Norse, Mayan, Japanese, Chinese. You name it."

Stiles almost laughed. "Completely useless for the real world, but an awesome asset for Beacon Hills."

"This is the real world."

"Terrifying, isn't it."

"We're gonna figure this out, Stiles. We'll find a way to stop the nogitsune, and save you."

"I know you will. I just hate that I can't do anything to help."

"You're taking this all really well."

Stiles shook his head. "I'm really not. I'm just so tired and I don't know what to do anymore."

"Go home and get some rest."

"I can't. I can't tell my dad what's going on, and what if I go to sleep and this _thing_ wakes up. I could hurt him."

"Sleep here then," Derek said, guiding him toward the bed. "I'll keep an eye on you."

"No, I-"

"You need to rest. Your sleep deprivation is only making you weaker and it stronger. If you're going to fight back, you need your strength."

Stiles nodded and fell into the bed, allowing Derek to cover him in the warm, fluffy blanket.

"I'm not strong enough," Stiles said as he fell asleep. "I was never strong. That's how it got in, isn't it?"

"You're wrong, Stiles. You're the strongest person I know." But Stiles was too far gone to hear.

* * *

"How is Stiles?" Melissa asked Scott and Isaac over dinner one night. They haven't said much of anything about the current state of their search for the nogitsune, and in fact she knew nothing of Stiles' involvement, but she also hadn't heard of any recent hallucination or blackout episodes, and she hoped that meant that whatever was wrong had passed, at least for the time being.

Scott and Isaac shared a look.

"No, don't to that. That is exactly the same thing you and Stiles used to do right before you would lie to me. Is Stiles okay?"

"We don't know," Isaac said.

"Is he getting worse? Blackouts? Hallucinations, fatigue, insomnia?"

"All of the above. He's..."

"Posessed," Scott finished. "He's posessed by a dark spirit. Sometimes it's controlling him, making him do things he's not aware of."

"Does this have anything to do with... you know?"

"Sort of? It said that our ritual _opened the door_, but that it's been there for a while."

Melissa frowned in thought. "How long is 'a while'?"

"It didn't say, just..." Scott trailed off and looked at her strangely. "You know something, don't you?"

"Scott-"

"No, you do know something. What is it?"

"Doctor-patient confidentiality; you know I can't tell you anything."

"_Mom_! This could literally save his live. All our lives."

Melissa sighed, weighing her options. "I'll get you a copy of the files tomorrow."

* * *

Scott didn't know what to do with the information he learned from his mom, but thankfully, Derek did.

"You knew Claudia Stilinski, didn't you?" he asked Peter.

"Depends on how you define 'knew'."

"Did you know her, or not?" Derek asked, suppressing a growl.

"We may have dated. Oh, wipe that look off your face. It was long before she and the precious sheriff were an item, so you don't have to worry your pretty little head, there was nothing scandalous about our relationship." Derek refused to believe Peter was capable of anything that wasn't at least a little scandalous. "Why do you ask?"

"What do you know about her death?"

"I know she died."

Derek glared.

"You know, that was much more frightening when you weren't a measley beta." Derek continued to glare. Peter sighed. "Fine. I know there were some strange circumstances surrounding her death. Talia kept a close eye on her near the end. Claudia and I may have parted ways, but she remained a close family friend."

"Did she know about us?"

"Of course."

"What was she?"

"What is this, twenty questions? She was a remarkable creature, and I sorely regret the day I let her slip away from me."

"_Was she human_?" Derek asked, correcting his previous question.

Peter pondered that one for a moment. "For the most part."

"_For the most part_," he repeated. "What does that mean?"

"It means that some people have a... predisposition, if you will. She was nothing like us, nothing different. But she was special. She could see us for what we were. What is that old phrase 'he who runs with wolves, learns to howl'? She, much like her son, _learned to howl_. People like them are drawn to the supernatural. It isn't just a fluke in their personality, it's a law of their biology. They can't escape us."

"Tell me everything you know about her death."

* * *

Stiles showed up on his doorstep early the next morning, but Derek almost didn't recognize his scent because all he could smell was...

Blood.

He quickly threw the door open, his eyes wide.

"Don't worry, it's not mine," Stiles said. Derek knew that much. "Or, maybe that should worry you more." He looked up at Derek with a look of fear.

"What happened?" he asked, pulling Stiles into the loft carefully.

Stiles shook his head. He wasn't sure what happened. "I think I hurt someone... Derek, I think I killed someone."

He looked like he was going to start crying at any second.

"Come on," Derek said, taking his hand and pulling him. "Let's get you cleaned up." He guided him into the bathroom and turned the shower on for him. "I'll go find you something else to wear," he said, then left him with some privacy.

When he returned a few minutes later, he found Stiles sitting on the floor of the shower, still fully clothed. The water running around him was stained with blood, but it was clear it would never fully wash out of his clothes.

"Stiles," was all he could say. He looked so helpless. And it made Derek feel helpless.

He helped Stiles get back to his feet, and started unbuttoning his shirt.

"When I imagined you undressing me, this isn't exactly how I pictured it," Stiles said, trying to lighten the mood. Derek, however, remained silent.

"Clean up," he said a few moments later, nudging him back under the water. "Clean clothes are on the sink."

"Thanks, Derek," Stiles said softly as the wolf left the room.

Twenty minutes later he stepped out of the shower, still not feeling clean, but he was certain he would never be able to fully scrub the feeling of blood off himself. He pulled on the clothes Derek had left for him. He felt a little silly, because the shirt was several sizes too big and the sweatpants were baggy, but they smelled like Derek and he found some small bit of comfort in that.

When he finally walked out of the bathroom, he found Derek in the kitchen making breakfast. One of his Japanese books was sitting open on the counter.

"He's smart _and_ he cooks," Stiles found himself saying.

"I'm a man of endless surprises."

Stiles almost laughed.

"What did you do with my clothes?" he asked, after taking a look around the loft.

"Burned them." In any other universe, that might have sounded like a joke, but in this one it was completely serious. Derek handed him a plate full of eggs, toast, and bacon.

"What did I do to deserve the VIP treatment?"

"You're here at 5 o'clock in the morning. Which means you're still afraid of going home. I assume that also means you aren't eating, or sleeping."

He assumed right, but Stiles refused to admit it.

"Eat your breakfast, then get some sleep. You can stay as long as you need."

"I can't keep taking over your room. You need to sleep too, you know."

"I'll be fine."

"At the very least, we can share," Stiles said. Derek raised an eyebrow. "That's not what I mean. No funny business. It just not fair that I completely steal your bed from you. Especially when you're being so nice. Which is terrifying, by the way."

"More or less terrifying than when I threatened to rip out your throat."

"More. Definitely more."

"You are a strange individual."

After struggling to eat even half of the food on his place, Stiles retired to the bedroom, hoping that he might be able to get in at least a couple hours of sleep. Derek somewhat begrudgingly joined him. They each lay down on their sides, facing one another, and Derek watched as Stiles closed his eyes, and waited for his breathing to even. It never did.

"Derek?" Stiles asked, opening his eyes a little while later.

"Yeah?"

"I need you to do something for me."

"I've lent you my shower, my clothes, and my bed, and I made you breakfast. What more do you want?"

"I need you to kill me," he said in a voice that was entirely too calm for the words he was saying.

"_What?_"

"I'm not saying right now. Just... when the time comes."

"Stiles-"

"I'm not giving up. Not yet. But we both know there is a good chance the only way to stop this... this _thing_, is to kill me."

"Sounds an awful lot like giving up."

"I'm not. I'm just saying... when, _if_ it comes to it. If it comes down to me or someone else, I want you to know this is my choice. I don't want to keep hurting people."

"Why me?" Derek asked after he took a moment to process. He wasn't agreeing to anything, but he at least deserved to know why he drew the short straw.

"I can't ask any of the others. They all care too much. And you... don't. Besides, it's kind of poetic, don't you think."

Derek didn't ask what he meant by that.

* * *

Derek didn't sleep, but that didn't matter. He took comfort listening to Stiles' deep breaths and slowed heart rate, knowing that he was finally getting some sleep. He tried not to think about their conversation.

"It's ironic, isn't it," Stiles voice said, interrupting the quiet breathing. It was his voice, but it wasn't Stiles talking. "He thinks you don't care about him, but really it's you who cares most."

"Leave," Derek said.

"You wound me."

"_Get. Out._"

"No."

Derek knew better than to get into a fight with him. Stiles may not have been physically strong, but the spirit possessing him was ten times stronger than any of the wolves.

"I will find a way to get you out of him. Even if it means I have to die."

"That's what makes this all so funny! You would gladly die for him. But what if he's right? What if the only way to stop _me_ is to kill _him_? He thinks you could do it easily, but you're not so sure."

Derek got out of the bed and left the room. Stiles followed him.

"What are you even doing here?" Derek asked. "You could be in control full time, but you're not. You let him free more than half the day." Stiles shrugged. "Is it fun for you? Watching him fall apart? Watching us all fall apart around him?"

"Why do you think I haven't killed any of you yet?"

"You get off on it, don't you?"

"Killing people isn't half as fun as destroying them," Stiles cackled. "It's so much more fun this way. Watching you crack. Waiting for you to _beg_ for your deaths."

"Leave," Derek said.

"No."

"Leave, or I will."

"You go right on ahead."

Derek growled. He grabbed his leather jacket and left.

* * *

He didn't return to the loft until late that night, though he was sure Stiles, or rather the monster wearing Stiles, had left hours before.

"Oh, good, you're home," Peter said when he returned.

"What do you want?" Derek asked. He didn't have the energy for this.

"Oh, you're in a good mood, aren't you? Well, I have something that might help with that."

And for the first time, Peter offered up some information that was actually useful, without having it forced out of him.

* * *

"It thrives on your darkness, Stiles," Scott said. "All the anger and sadness you keep bottled up, you have to let it go, so it has nothing left to feed on."

Stiles clenched his teeth. "I don't think you get it Scott. I _can't._"

"Stiles-"

"No! I lost my _mom_. You have no idea what that feels like. Yeah, you're dad is absent and kind of a dick, but at least he's _alive_. That sadness doesn't just go away. You think I want to be sad about it all the time? Why do you think I try so hard to be happy? Because when I'm pretending at least it feels a little better. But that's all it is: pretending. It still hurts every day. If I knew how to let it go, trust me, I would. I would do it in a heartbeat, but I _can't_."

"You have to try."

Stiles wanted to scream. He wondered, briefly, if this was what Lydia felt.

He screamed.

It didn't really make him feel any better, and it didn't give him any kind of eye opening revelation, but it was silly to have expected as much. He wasn't Lydia.

"Do you feel better?"

"No."

"Stiles-"

"Just stop. I can't." He shook his head and walked away.

* * *

"Clearly this isn't going to be as easy as we had hoped," Peter said, after he and Derek received an update from Scott.

"You thought it would be?"

Peter silently pondered (or maybe he was just planning his next scheme), while Derek read from one of his mythology books. Or, tried reading. He was finding it difficult to focus.

"What would be your catharsis?" Peter asked after a while.

"What?"

"After everything that happened: Kate, the fire, _me_. What would be the one thing that could make it all hurt less? Your catharsis."

Derek was silent for a moment. "I already got it." He wasn't even sure he had realized it until just then, but yes, it hurt less than it used to, and he could pinpoint exactly what the cause was.

He jumped out of his chair and started rummaging through his pile of books, carelessly throwing aside the ones he didn't need.

"What are you doing?"

"I have an idea. Something I read a couple of weeks ago. It wasn't important at the time."

"And now it is?"

Derek held up a book with a picture of a screaming creature that looked suspiciously like death. "I have an idea," he said with look that Peter didn't like in the slightest.

"I am almost certain I'm going to hate this."

* * *

Derek and Peter avoided the loft for the next three days. If Stiles came around again, which he likely would, they could not risk that he would uncover any parts of their plan. If he did, it would be completely ruined. Only when they were certain they had worked everything out did they return.

Neither was surprised to find Stiles already there. He was sitting in the kitchen, his head resting on the counter. When he sat up, it was immediately clear that he had been crying.

"They found the bodies this morning," he said.

"You deal with your little pet's emotions," Peter said with a roll of his eyes. "I'll get started."

"What bodies?" Derek asked.

"I killed three people. An elderly couple and their daughter. God, she had a _kid_. He's going to grow up without her, because of _me_."

"Not you, Stiles. This thing that's controlling you, it's not you."

"But it's my hands. It's their blood on my hands."

"Stiles, _stop_. You have got to stop blaming yourself for things that are not your fault. Don't you see, your guilt is feeding it, making it stronger."

"_I'm almost set in here_," Peter called from the other room.

"What's he doing?" Stiles asked.

"We've come up with a plan," Derek said.

Stiles eyes widened. "Don't tell me that. You can't tell me these things. He'll catch on and find a way to stop you."

Derek shook his head. "No he won't." And then he kissed him.

It wasn't particularly wet or romantic. Derek's hands held tightly to either side of Stiles' face, and it was over before it really even began. It didn't feel like a declaration of any kind. In fact, it felt a bit like an apology.

"What was that for?"

"I'm sorry, Stiles," Peter said, appearing at his side. "But this is where we have to kill you."

There was a sudden sharp pain in the back of his neck, and then-

Nothing.

"What- what are you doing?" the dark spirit choked out. Peter's claws were in his neck, paralyzing him, as they dragged him across the apartment.

"Getting rid of you once and for all," Derek said.

"You can't kill me. You can't!"

"No. But Stiles can."

They set him over a symbol Peter had painted on the floor, trapping him within it's magic.

"Start it, now," Peter said. Derek crouched down to the book lying open on the floor and began to read the Latin aloud.

"What are you doing? Stop it?!" the spirit shrieked. It struggled against Peter, but he was already connected to Stiles' mind. It was too late to stop him.

* * *

_"Stiles?"_

_"Stiles, are you okay?"_

Stiles opened his eyes, but he felt groggy and out of touch.

_"Stiles. You have to wake up. We don't have a lot of time."_

"Mom?"

"_Hey sweetie._"

"Mom, what are you doing here?" He took a look at his surroundings. "And where exactly is here?"

She merely smiled at him.

"Am I... Am I dead?"

_"Not quite. As for where? I guess we can call it limbo."_

"So I'm, what, dying?"

_"Only if you let yourself."_

"What's going on?"

_"You're being given a choice. You can let the nogitsune win, or you can fight back. Either way, one of you must die."_

"But if I die... then I'll be with you."

_"Oh, Stiles."_ She shook her head. _"Those boys down there are fighting for you. And you're just going to give up? That's not why I'm here."_

"Then why are you here?"

_"Because they knew that what you need to hear can only be heard from me."_

"And what is it I need to hear?"

_"That I'm dead."_

"I think I actually figured that one out."

_"I'm dead, and I'm gone. It's time to stop grieving."_

"I don't know how."

_"Neither did I. And that's what killed me. I can't let the same thing happen to you. So I'm going to tell you a story. And at the end of that story, you are going to return to your family, and you're going to win this fight. You're going to live."_

Stiles didn't quite belive that there was anything she could say that could ease his pain. "So tell your story."

_"I had an older sister, you know. Her name was Sara, and I worshipped the ground she walked on. She practically raised me after our parents died. Then one day when I was almost sixteen, she took me out to teach me to drive. A truck driver feel asleep at the wheel and hit us. Sara died instantly. And I never got over it._

_"A few weeks later, a little girl was brought into the hospital where I volunteered. She was an orphan, maybe eight years old, and she reminded me so much of Sara. So I kept her company. When the Hales found out... they told me to stay away from her."_

"The Hales?" Stiles asked. She had known them?

_"They were like family. I should have listened to them. Seeing people like them, wolves, afraid of this girl, I should have listened to them. But she was just a little girl, and I thought it was funny they were so frightened by someone so harmless."_

"She wasn't harmless, was she?"

_"They could see what I couldn't. The darkness controlling her. I was with her when she died. And my grief over Sara, over our parents... it gave the nogitsune someone else to latch onto. That's what it does. Finds a grieving host, sits there for a while, growing in the back of your mind, until it has enough power to take over. That's what it did to me. Now it's doing the same to you. The difference is, you can fight it."_

"Scott said I have to let go of my sadness."

_"He's right."_

"I don't know how."

_"Stop clinging to the past and embrace your future. Just because I'm gone doesn't mean I'm not with you. I am always watching out for you." She stopped and looked around. The sky was growing dark. "Our time is almost up. You have to go back. Go back to your dad, and your friends, and that boy who loves you. They need you. They need you to live."_

Stiles rushed forward, wrapping his arms rightly around her.

_"I love you, Stiles,"_ she said.

"I love you, mom," he sobbed.

And then he let go.

* * *

"Stiles?" a fuzzy voice said.

Stiles moaned as he tried to open his eyes. "Dad?"

"Hey kiddo. How you feeling?"

"Like I was trampled by a million puppy sized elephants," he said. "What happened?"

"From what I understand there's been one hell of a fight going on in your noggin. You've been out for almost three days."

"Three days?"

"Yep. Got a lot of people waiting to see you."

"Think they can wait until my headache is gone?"

"I'm sure they can," he said with a smile. He patted Stiles' hand, glad to know that he was okay.

* * *

"'Bout time you came around," Stiles said when Derek finally came to visit. He had been awake and in observation for two days, and everyone else had come by to visit at least once already.

Derek shrugged, unsure what to say. "I thought you might be a little mad, after we kind of killed you and all."

"Well, clearly you're an idiot."

Derek frowned.

"Oh, would you just come over here and kiss me already?" Stiles said. Then, as an afterthought, he added. "I mean, if you want to. It's not required or anything. But I'm just saying that I would be very okay if you did."

He did.


End file.
